This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The general objective of this research project is to develop ultra-sensitive MRI probes. One approach is based on MFe2O4 (M=Fe, Co Mn)-loaded polymer micelles for cancer molecular imaging applications. The low sensitivity of conventional MR contrast agents severely limits their use for monitoring molecular processes in vivo. Another approach is to used superparamagnetic iron oxide nanoparticles (SPIO). The growing use of SPIO in molecular imaging, cell tracking and biomolecular detection has resulted in the rapid development of novel SPIO formulations and imaging acquisition methods. Compared to the low molecular weight, paramagnetic metal chelates such as Gd-DTPA (T1 contrast agent), SPIO nanoparticles are considered T2-negative contrast agents with substantially higher T1 and T2 relaxivity. Conventionally, SPIO particles are evaluated by T2- or T2*-weighted MR imaging for their abilities in dephasing water signals. Image void at high SPIO concentrations and requirement of a pre-contrast scan limit the accuracy and specificity for SPIO detection. A recent objective is to develop and apply an off-resonance saturation (ORS) method to allow for on-and-off imaging of [unreadable]v[unreadable]3-targeted SPIO-loaded polymeric micelles for molecular imaging of solid tumors. The RR has provided access to the 4.7 T, the workhorse for us. Iniitially the imaging was performed by Dr. Jimin Ren, supported by the Research Resource. Dr. Ren trained two post - doctoral fellows, Drs. Charlie Khemtong and Chase Kessinger, and now all imaging is performed by Dr. Gao's team.